1. Field of the Invention
The present invention relates to document processing machines and, more particularly, to document processing machines incorporating control systems.
2. Prior Art
Various document systems require that an automatic document handling apparatus within the system operate within precision tolerances so as to align a particular edge of a document with a given coordinate. For example, in an x-y coordinate system this could be the coordinates 0,0, on a copier platen where the scanner or copier optics have also been aligned to begin imaging at the 0,0 coordinates on the copier platen. This process of aligning the document relative to a given coordinate is known as document registration. In a manual copying operation, an original document is registered by the user with ruler markings along the sides of the platen. In systems having automatic document handling systems document registration is automatic and is generally accomplished by the use of various belts, rollers and sensors situated along the document path. The precision control of the various belts and rollers along the document path is generally accomplished using classical feedback control systems. If the original document is not properly registered then undesirable dark borders and shadow images may appear on the copy. In addition to document registration other document positioning functions requiring feedback control includes photo receptive (PR) drum motion control, and intermediate belt transfer (IBT) motion control, and developer motion control. In general, the desired positioning accuracy for document handling is on the order of one millimeter. As is readily appreciated an automatic document handling system must rapidly and accurately position each document. Conventional feedback control systems correct for the undesired linear motion of the document handling systems. However, the non-linear motion due to motor torque ripple, gear run-out, and roll run-out can not always be corrected due to bandwidth limitations in the classical controller. Currently, the non-linear motion due to these errors is minimized by demanding that tolerances associated with manufactured parts be as small as possible. Achieving such tolerances are difficult and expensive to maintain.
In accordance with one embodiment of the invention, a non-linear control (NLC) system for controlling performance of a device is provided. The NLC system comprises a controller system with a first and second feedback compensator connected to the controller. The first feedback compensator compensates for linear error performance of the device while the second feedback compensator compensates for non-linear error performance of the device.
In accordance with another embodiment, the invention includes a method for controlling non-linear motion of a system. The method comprises the steps of sampling non-linear performance of the system and determining at least one frequency component of the sampled non-linear performance. Next, at least one sinusoid substantially equal in magnitude to the at least one frequency component and substantially 180 degrees phase inverted with respect to the at least one frequency component is applied to the system controller.
Another embodiment of the invention is directed towards a hybrid learning feedback controller (HLC) system for controlling operation of a xerographic imaging device; the xerographic imaging device having an input port and an output port. The HLC feedback controller system comprises a feed forward controller system operative to receive an actuating signal and in response to the actuating signal output a manipulated variable. The feed forward controller comprises a feed forward controller, a first input summing node, a second input summing node, a first proportionality device, and a second feedback compensator having a learning controller system for correcting non-linear motion of the device.